how to use multiple combobox

hi,
In my project i need to use 3 comboboxes.First combo contain years from Db and after seleting one year from 1st combo ,account names related to that year will populate on 2nd combobox.then after selecting account name from 2nd combo,filenames related to that year and that account name will populate in 3rd combobox.finally i want data based on year,accountname, filename.
i'am getting all years in 1st combo but not able to populate 2nd and 3rd combos.
Regards,
vanisri